1. Field
The present disclosure relates generally to aircraft and, in particular, to a method and apparatus for a helicopter assembly. Still more particularly, the present disclosure relates to a method and apparatus for an assembly that connects a helicopter rotor blade to a hub.
2. Background
The rotor system of a helicopter may be the rotating part of a helicopter that generates lift. A rotor system may be mounted horizontally to provide vertical lift. In some cases, a tilt rotor may be used in which the rotor may be mounted on a pylon that may rotate from a horizontal plane to a vertical plane. A rotor system may include a hub and rotor blades. The hub may provide an attachment point for rotor blades. The rotor blades may be attached to the hub using various methods.
For example, without limitation, rotor blades may be connected to the hub in a rigid manner. With this type of rotor system, the blades are not hinged in the flap or drag axes but may be feathered in order to vary thrust and cyclic blade pitch.
Another type of rotor system is a semi-rigid rotor system. With this type of rotor system, flapping and feathering may occur. The blades may be rigidly attached to the hub. The hub may then be attached to a mast in which the hub may tilt with respect to the shaft.
With a fully articulated rotor system, each blade may be attached to the hub through a number of hinges. These hinges may allow a blade to move independently of the other blades. The independent movement may be such that the blades may change pitch but do not change location relative to the rotational axis of the rotor. These types of rotor systems may allow the blades to flap, feather, lead, lag, and/or otherwise move independently of the other blades.
With fully articulated rotor systems, different types of architectures may be used to connect the blades to the hub. For example, without limitation, a bearing-based connection system or a bearingless connection system may be used. With a bearingless connection system, a flexible structural member may be used to connect and/or retain a blade to a hub in a rotor system. This flexible structural member may allow a capability to control the position of a blade in an accurate manner. These positions may allow for motions such as, for example, without limitation, flap wise bending motions, end wise bending motions, torsional change motions, or other suitable motions.
The flexible structural member may replace older designs, which may use a hinge and/or journal-type bearings at the connection of the blade to the hub. This type of design may also be referred to as a flex beam or flex beam connector.
When replacing an older rotor assembly with a flex beam assembly, it may be desirable to keep the different dimensions, materials, and/or other suitable features of the current system as close to the original design as possible. This type of goal may be desirable to maintain performance in other flight features from the original design. With these types of requirements, changing a bearing-based rotor system to a bearingless rotor system may be challenging to maintain as many structural parameters as possible close to original design specifications.
Therefore, it would be advantageous to have a method and apparatus for assembling a rotor system that overcomes the issues described above as well as possibly other issues.